Presence and chat applications (e.g. ICQ on the Internet) are gaining popularity. These applications are based on that the users register their presence and may be visible on other users contact or buddy lists. An example of such an application is ICQ. ICQ is a presence and chat service on the Internet. ICQ allows you to know which of your friends that are online, and you may use a variety of communication techniques to contact them. It is also integrated with Microsoft NetMeeting.
This is for the time being the most common application, but other presence applications are expected to be common in the near future. An example of such an application is a localization application by which a group of users are informed e.g. via a map on a terminal screen where the other users currently are positioned. The positions may be provided by a GPS receiver placed in each user's terminal. Especially this last mentioned application or similar applications are expected to become popular services, and therefore, presence application will probably occur in an increasing number of associations.
As also IP telephony becomes more customary, it is clear that there is a need for solutions implementing presence applications therein. H.323 is today one of the most widespread protocol for IP telephony or more generally for multimedia communication where the underlying transport is a Packet Based Network. The description in this application is applied to this protocol, and associated terminology, well known to persons skilled in the art, will be used.
According to the H.323 standard, user registration into a network is arranged by so-called Gatekeepers.
The H.323 protocol describes/provides the procedure for the user registration. The user registration is basically a relation between the user identifiers (called aliases in H.323) e.g. E.164 numbers or e-mail addresses and the users current IP address. See FIG. 1.
When a User A registers into the H.323 based system, its endpoint, representing the users terminal, sends the information about the IP address associated with that endpoint. This information is encapsulated in a registration request message (RRQ) and sent to a H323 Gatekeeper (GK) (1). The relevant information from the RRQ message is then stored in a dB (2). As an acknowledgement to the user about its registration, the GK responds with a registration confirmation message (RCF), (3). This is a normal registering procedure in H.323 based systems.
The User A is now recognised within the system under aliases E164: 523 946, e-mail: userA@ipt.com and can be contacted on IP:111.12.11.17.
H.323 is based on users registering into a network, but there is currently no way to provide the already existing registration status (presence) to other users in the H.323. Consequently, there is currently no way other users can find out if User A is registered or not, and User A can not notify his friends about his/hers presence in the system using H.323.
ICQ is a presence and chat service on the Internet. ICQ allows you to know which of your friends that are online, and you may use a variety of communication techniques to contact them. It is also integrated with Microsoft NetMeeting, which in fact is a H.323 endpoint.
However, if you want to be registered into a H.323 network, you would have to register both in ICQ and the H.323 network, and you will not know if other users registered in ICQ also are registered in a H.323 network. ICQ does not make use of the information already stored in the Gatekeepers whether a user is logged in or not.
SIP is another protocol that may be used for IP telephony. SIP, like H.323, uses registrations to map user identifiers to host names and thereby IP addresses. SIP has proposed extensions for presence handling. The mechanism is based on that a user may send a SUBSCRIBE message to subscribe to other users registrations, and will get a NOTIFY message when one of these users changes his/her registration status.
However, this is a mechanism for SIP protocol, and is not applicable for equipment using the H.323 protocol. Therefore, none of the above mentioned known solutions solve the problem of relating presence information to registration status in an H.323 network.